1. Field of the Invention
The present invention relates to an optical pickup for use in a disk player such as a DVD, and more particularly to an optical pickup which exhibits high performance and is inexpensive, and in which a read error is prevented from occurring.
2. Description of the Related Art
As techniques of an optical pickup, those disclosed in JP-A-8-7321 and the like are known, and one example of it will be described with reference to FIG. 6. In this optical pickup, a photodiode PD is disposed at an opening 3a in one end of a light passage hole 3 with a half mirror 2 in a pickup body 1, while a collimator lens QWP and an objective lens OL are disposed at an opening 3b in the other end thereof. A semiconductor laser LD is accommodated in a branching hole 4 formed in a side surface of the pickup body 1, and a printed circuit board 6 connected to the photodiode PD and the semiconductor laser LD by means of flexible cables 5 is secured to an outer peripheral surface of the pickup body 1 by means of a screw 7. It should be noted that reference numeral 8 denotes a supporting baseplate of the semiconductor laser LD, and reference numeral 9 denotes a connector secured to the printed circuit board 6. As a plug 10 is connected to the connector 9, the photodiode PD and the semiconductor laser LD are connected to a control unit of a microcomputer or the like.
In the above-described configuration, laser light is projected from the semiconductor laser LD onto a disk D via the half mirror 2, the collimator lens QWP, and the objective lens OL, and the reflected light is received by the photodiode PD through the half mirror 2, thereby making it possible to read information recorded on the disk D.
The problem encountered here is that the semiconductor laser LD generates heat due to the projection of the laser light, resulting in a decline its capability. Accordingly, the pickup body 1 is conventionally formed by aluminum die casting to promote the dissipation of heat, but the aluminum die-cast pickup body 1 is expensive.
Accordingly, it has been conceived to form the pickup body 1 of an inexpensive hard synthetic resin and to use a metal plate for the supporting baseplate 8 of the semiconductor laser LD, so as to promote the dissipation of heat.
In the above-described configuration, the arrangement provided is such that the dissipation of heat is promoted by the metallic supporting baseplate 8 of the semiconductor laser LD. If the supporting baseplate 8 is made large to enhance the heat dissipation effect, the supporting baseplate 8 becomes bulky and comes into contact with peripheral devices, so that there is a limit to making it large. If a high-performance device is used as the semiconductor laser LD, the amount of heat generated is large, so that the pickup body 1 becomes thermally expanded and deformed (see the phantom line in FIG. 6). Hence, there is a possibility that an optical axis O connecting the photodiode PD and the objective lens OL may become curved, possibly resulting in the occurrence of a read error. Accordingly, as the semiconductor laser LD, it is inevitable to use one which generates a small amount of heat, with the result that the range of selection is bound to be narrow.